Silver halide nucleating compositions containing ionic boron hydrides

ABSTRACT

IONIC BORON HYDRIDES HAVING AT LEAST TWO BORON ATOMS PER MOLECULE, SUCH AS, FOR EXAMPLE, TETRAMETHYLAMMONIUM OCTAHYDROTRIBORATE, ARE EFFECTIVE SILVER HALIDE NUCLEATING AGENTS FOR USE IN NUCLEATING BATHS OR DEVELOPER SOLUTIONS EMPLOYED IN PHOTOGRAPHIC PROCESSING. THESE COMPOUNDS ARE SUPERIOR NUCLEATING AGENTS, AS COMPARED TO THE ALKALI METAL BOROHYDRIDES OR THE BORANES USED HERETOFORE FOR THIS PURPOSE, WITH RESPECT TO SUCH FACTORS AS STABILITY IN SOLUTION, EASE OF PROCESS CONTROL, AND IMPROVED SENSITOMETRIC RESULTS.

United St e at o 3,554,748 SILVER HALIDE NUCLEATING COMPOSITIONS CONTAINING IONIC BORON HYDRIDES Charleton C. Bard and Howard W. Vogt, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Dec. 28, 1966, Ser. No. 605,220

Int. Cl. G03c 7/16, /50, 5/30 U.S. Cl. 96-22 v t 15 Claims ABSTRACT OF THE DISCLOSURE This invention relates to compositions for photographic processing and to the reversal processing of photographic silver halide emulsions.

It is known that in the reversal processing of photographic silver halide emulsions the exposed emulsion is usually subjected to a first (negative) developer followed by reversal re-exposure and subsequent positive image development.

Elimination of the reversal exposure step in processing photographic silver halide emulsions is a desirable improvement, particularly for multilayer color elements, Certain nucleating agents that have been used in alkaline solutions after the first'development and before the color development in place of the reversal re-exposure step, have not been as stable as desired at the pHs required in the color developer. The use of amine boranes described by Hanson and Vogt US. Pat. 3,246,987, as nucleating agents in 'photographic processing solutions produced a valuable technical advance over the alkali metal borohydrides in that the former compounds are substantially;

more stable than the alkali metal borohydrides. The amine boranes, however, tend to release free amines when they decompose or react in a processing solution and these amines are well known to be effective silver halide solvents that cause fog. When amine boranes are incorporated in color developers in a reversal process, this decomposition to free amines frequently results in a loss of image density in the low density portion of an image reproduction in one or more of the layers of a multilayer color element. The process also becomes very sensitive to the concentration of the amine borane in the color developer. In addition, the amine borane frequently reacts in an unknown way with constituent(s) present in typical color developers so that the amine boranes are dissipated from solution and thus cause serious chemical control problems in a reversal color process. It is therefore an object of our invention to provide novel nucleating agents which have greatly improved stability in aqueous processing solutions at pHs from about 3 to about 13.

Another object is to provide novel compositions for preparing nucleating baths for reversal photographic processing.

Another object is to provide novel nucleating compositions for preparing color developer solutions for reversal color processing.

Another object is to provide novel nucleating color developer solutions that have substantially greater stability than prior art nucleating color developer solutions.

Another object is to provide novel reversal photographic color processes that are relatively insensitive to the concentration of our novel boron hydride nucleating agents in our color developer solutions.

Another object is to provide novel reversal photographic color processes using our nucleating color developer solutions which do not produce the objectionable loss in image density in the low density regions of the image reproduction, i.e., the toe regions of a sensitometric curve relating developed image density to log of the exposure.

These and still other objects which will become apparent from the following specification and claims are accomplished by the use of our invention.

According to our invention, ionic boron hydrides having at least 2 boron atoms per molecule are used as novel nucleating agents in compositions used to advantage for preparing nucleating baths and positive image developing baths in reversal photographic processes. In their simplest form, our novel nucleating compositions contain one or more ionic boron hydrides having at least 2 boron atoms per molecule and a buffer, preferably capable of buffering in the pH range from about 3 to about 13. Photographic silver halide developing agents are also advantageously incorporated in our compositions.

Included among the ionic boron hydrides of our invention are those having the formula:

wherein M represents a positive ion derived from nitrogen, for example, an ammonium ion, e.g., ammonium, quaternary ammonium(e.g., a tetraalkyl ammonium with alkyl groups having from 1 to 18 carbon atoms, such as, tetramethylammonium, tetraethylammonium, tetrabutylammonium, trimethyl-octadecylammoniu-m, etc., heterocyclic quaternary ammonium having from 5 to 6 members in the ring, such as, thiazolium, oxazoliurn, imidazoium, indolium, pyridinium, quinolinium, pyrrolinium, pyrrolidinium, etc.), sulfur, e.g., ternary sulfonium (e.g., trimethylsulfonium, triethylsulfonium, etc.), phosphorus, e.g., quaternary phosphonium (e.g., tetramethylphosphonium, tetraethylphosphonium, etc.), arsenic, e. g., quaternary arsonium (e.g., tetramethylarsonium, tetraethylarsonium, etc.), antimony, e.g., quaternary stibonium (e.g., tetramethylstibonium, tetraethylstibonium, etc.), an alkali metal (e.g., sodium, potassium, lithium, etc.), an alkaline earth metal (e.g., calcium, barium, strontium, magnesium,

7 etc.; 0 is an integer greater than 0, preferably from 1 to 3;

x is an integer greater than 0, preferably from 1 to 2; y is an integer greater than 1, preferably an integer from 2 to 20; and z is an integer greater than 4, preferably an integer from 6 to 14.

'Included among the boron hydrides of our invention are the following typical representative examples.

(1) Tetramethylammonium octahydrotriborate (2) Di-tetramethylammonium hexahydrodiborate (3) Di-tetramethylammonium enneahydropentaborate I (4) Di-tetramethylammonium tetradecahydrodecaborate (5) Trimethyl-octadecylammonium octahydrotriborate (6) Pyridinium octahydrotriborate (7) Tetramethylphosphonium octahydrotriborate (8) Trimethylsulfonium octahydrotriborate (9) Di-sodium hexahydrodiborate (10) Barium hexahydrodiborate (l1) Di-sodium enneahydropentaborate 12) Di-lithium-tetradecahydrodecaborate (13) Di-sodium tetradecahydrodecaborate (14) Magnesium hexahydrodiborate Any of the buffering materials commonly used in photographic processing solutions are used advantageously in our compositions. These buffers include phosphoric acid, alkali metal phosphates, sulfuric acid, phosphorous acid, alkali metal phosphites, boric acid, alkali metal carbonates, alkali metal acetates, acetic acid, maleic acid, alkali metal maleates, etc.

Silver halide developing agents used to advantage in our compositions include any of the well known blackand-white developers such as the 3-pyrazolidones, e.g., l-phenyl 3 pyrazolidone, 4-methyl-1-phenyl-3-pyrazolidone, 4,4 dimethyl-1-phenyl-3-pyrazolidone, etc., hydroquinone, p-methylamino phenol, 2,4-diamino phenol, etc., and any of the well-known color develo ing primary aromatic amino developing agents including the phenylene diamines and substituted derivatives. Typical of such colorforming developers are the sulfonamido-substituted pphenylenediamines disclosed in Weissberger US. Pat. 2,548,574, issued Apr. 10, 1951, the substituted p-phenylenediamines disclosed in Weissberger et al., US. Pat. 2,552,240-2, issued Ma 8, 1951, and the substituted pphenylenediamines disclosed in Weissberger et al., US. Pat. 2,566,271, issued Aug. 28, 1951. Other phenylenediamine color-forming developers can be employed to like advantage in the process of our invention.

In addition, our compositions advantageously contain any other of the addenda conventionally used in photographic reversal developers including alkali metal sulfites, alkali metal halides, alkali metal hydroxides, citrazinic acid, ethylene diamine, benzyl alcohol, water softening agents such as sodium hexametaphosphate, competing developing agents, etc.

Our compositions are advantageously packaged in dry form, preferably in a suitable container which will protect the materials from moisture. Alternatively the materials may be packaged as stock solutions which are diluted to produce the working solutions for use in the photographic processing machine.

Our boron hydrides have the following unique advantages over the prior art alkali metal borohydrides and amine boranes:

(1) They are more stable when incorporated in color developer solutions;

(2) They do not give objectionable image density loss in low density or toe region of the sensitometric curve of reversal type films; and

(3) The reversal color processes in which they are used are relatively insensitive to the concentration of our boron hydrides over wide concentration ranges. Use of our compositions in reversal processes not only produces improved sensitometric results but provides a process which is substantially easier to control.

Our compositions generally contain sufiicient boron hydrides to produce a concentration of from about 10 to about 10,000 milligrams per liter, preferably in the range from about 70 to about 400 milligrams per liter when dissolved in water and sufficient buffer to maintain the pH at the desired level within the range from about 3 to about 13. When our compositions include a silver halide developing agent, sufiicient developing agent is used to produce a concentration in the solution of from about 0.5

7 gram per liter to about 15 grams per liter. The optimum 4 processed, the processing conditions, etc., and can readily be determined by methods well known in the art.

In the reversal processing of multilayer, multicolor photographic elements, the first developer forms a negative black-and-white image. Photographic elements of the multilayer, multicolor type which do not contain colorforming couplers in the silver halide emulsion layers then are given a selective reversal re-exposure of one silver halide emulsion layer at a time followed by color development of the reversal exposed layer with a color developer containing a color-forming coupler which reacts with the oxidized p-phenylenediamine type developer to form the appropriate dye image corresponding to the positive silver image formed. After selective reversal re-exposure and color development of one layer, a second layer is selectively reversal re-exposed and color developed then the third layer is selectively reversal re-exposed and color developed. The silver images and remaining silver halide are then removed by bleaching and fixing to leave the three dye images. The nucleating agents of our invention are use to advantage to eliminate the reversal re-exposure required for the last color development step. For this purpose, the nucleating agents are either used in a nucleating bath to which the film is contacted after the second color image is color developed and before the third color image is developed or alternatively the nucleating agent is incorporated in the color developer used to develop the third color image.

Particularly useful color films for reversal processing according to the method of our invention are films comprising a conventional support, such as cellulose esters, glass, polyester film, polyvinyl acetal film, polycarbonate film, etc., having coated thereon at least two silver halide layers which have been sensitized to particular regions of the spectrum. These emulsions have incorporated therein the color-forming components or couplers, which combine with the oxidation products of the photographic color developers, to produce the desired color images. For example, a typical color film, useful in practicing our invention comprises a support having coated thereon a red-sensitized photographic silver halide emulsion having incorporated therein a coupler for the cyan image (e.g., a phenolic coupler), a green-sensitized photographic silver halide emulsion having incorporated therein a coupler for the magenta image (e.g., pyrazolone coupler), and a blue-sensitized photographic silver halide emulsion containing a coupler for the yellow image (e .g., a coupler containing an open-chain ketomethylene group). The photographic element can also contain conventional interlayers and filter layers, such as a yellow filter layer beneath the blue-sensitized emulsion to prevent exposure by blue light to either the redor green-sensitized emulsion. Photographic color films of the immediate type can be processed by a technique requiring fewer steps than the processing of color films of the multilayer, multicolor type mentioned above. For the processing of the emulsions having coupler compounds incorporated therein, it is only necessary to treat the exposed color film with the usual type of black-and-white developer for producing a negative silver image, followed by treatment with the aqueous nucleating solution and followed by conventional color developer or alternatively, followed by treatment with the color developer to which has been added one of our nucleating agents.

Our compositions containing our boron hydride compounds and buffer agent are also used to advantage in black-and-white reversal processes. In a black-and-white process, the negative developer is followed by a water wash, a bleach, a clearing bath, water wash, aqueous nucleating bath prepared from our composition and positive development. Alternatively, our composition may be used to prepare positive developer solutions which include our nucleating agent so that no separate nucleating bath is required. Our nucleating agents are also used advantageously as the sole developing agent in the re= versal developer of a reversal black-and-white process.

The following typical examples will further illustrate our invention. v v

- EXAMPLE -1 A composition was prepared consisting of 100 milli grams of tetramethylammonium octahydrotriborate and 36 grams of trisodium phosphate-EH 0. Color Developer 1 (of our invention was made by adding the above composition to one liter of an aqueous solution containing the following chemicals:

Sodium hexametaphosphate-5.0 grams I 4-amino-N-ethyl-N-(fl-methane sulfonamido ethyl)-mtoluidine .sesquisulfate monohydrate10.5 grams 1 Benzyl alcohol-31 milliliters Ethylenediamine 3 grams Citrazinic acid1.35 grams Sodium sulfite7.6 grams Sodium bromide0.8 gram Potassium iodide-J8 milligrams Sodium hydroxide--2.05 grams Water to make1' l iter The completed solution'had a pH of 11.25 at 80 F. Color Developer 2 (outside our invention) was made identical to Developer '1 except that the 100 milligrams of tetramethylammonium octahydrotriborate were replaced with 100 milligrams of t-butyl amine borane Ii)3 2' 3 I I outside our invention]. v

Color Developer 3 (outside our invention) was made identical to Developer 1 excepting that the 100 milligrams of tetramethylammonium octahydrotriborate was replaced with 100- milligrams of sodium borohydride (NaBH outside our invention). These 3 color developer solutions were stored and the amount of the nucleating agent was analytically determined periodically in samples taken from thesolutions in order to determine the /2 life (t /2)'of thechemical nucleating agent in each of the solutions.' Our Color Developer 1 had a /2 life of more than 100 days while hydroqu inone negativedeveloper; water washingyharde'm ing in a conventional potassium chrome alum hardening bath; water washing; color development'in our Color Developer 1 (described in Example 1); water washing; clearing and fixing in a conventional sodium thiosulfate, sodium bisulfite bath; then bleaching in a'conventional potassium dichromate, potassium ferricyanide, potassium bromide bleach solution; water washing; clearing and fixing in the conventional sodium thiosulfite bisulfite bath; water washing; and stabilization in a formaldehyde solution. Excepting for the color developer, the solutions were the same as used in Example 1 of US. Pat. 3,246,987.

Another piece er the same multicolor element was given the same exposure and processed as described above except that Color Developer 2 (described in Exa le 1 outside the invention'was used. v

The developed image densities were determined and the sensitometric curves relating image density vs. log exposure were plotted for each of the two processed color elements. The sensitometric curve for the color element that was color developed in our Color Developer 1 had the desired characterisics including a normal contrast in the toe or low density region of the curve, while the sensitometric curve for the color element processed in Color Developer 2, outside our invention, had a deficiency in image density in the low density region of the curve indicating a very contrasty image that was highly objectionable.

This example was repeated using various concentrations of the nucleating agents and it was found that optimum nucleation was achieved at about 70 milligrams per liter. Increases of only 30 milligrams of t-butyl amine borane per liter above the optimum level gave unacceptable photographic results, while increases of milligrams per liter of tetramethylammonium octahydrotriborate above the optimum showed little or no change from the optimum sensitometric results. This example illustrates the technical advance provided by use of our compositions in reversal color processing.

Similar results are obtained by using the other nucleating agents of our invention as described by Formula 1 including the nucleating agents 2 through 14 specifically named previously in the specification when they are used in our compositions to make the above color developer solutions or other color developing solutions used advantageously in color reversal processes.

EXAMPLE 3 A composition was prepared containing milligrams of tetramethylammonium octahydrotriborate and 1.5 grams of sodium hydroxide. This composition was dissolved in one liter of water containing one gram of sodium hexametaphosphate to produce a nucleating bath.

A photographic multilayer color element such as was described in Example 2 was exposed and processed as in Example 2 excepting that the above described nucleating .bath was inserted in the process after the potassium chrome hardening bath and before the Color Developer Solution which in this example did not contain any nucleating agent.

Example 3 was repeated using in place of our nucleating bath a nucleating bath using 150 milligrams of 2- butylamine borane.

The developed image densities were measured and sensitometric curves relating the densities with the log exposure were plotted for the cyan, magenta and yellow dyes in each of the processed color elements. A comparison of the sensitometric curves showed that the cyan and magenta maximum densities for the two elements were very close indicating full reversal while the yellow scale contains more yellow dye due to less reduction of the top layer silver halide by the tetramethylammonium octahydrotriborate as compared to t-butylamine borane. This example still further illustrates the advantages provided by use of our compositions.

EXAMPLE 4 Our compositions are used advantageously to prepare nucleating baths such as are described by Example 3 (containing any of our nucleating agents of Formula I) in a conventional color reversal process in which separate reversal color-forming develop solutions containing couplers are used to produce the cyan, yellow, and magenta dye images. In this process our nucleating bath is used in the process between the wash following the yellow color developer and immediately before the magenta developer. The advantages illustrated in the preceding examples are also demonstrated in this example. 7

Similarly, our compositions are used advantageously to make nucleating baths for use in reversal black-and-white processes and alternatively the compositions can be used to make a reversal developer solution that contains the nucleating agent so that no separate nucleating bath (or reversal re-exposure) is needed.

The ionic boron hydrides of our invention are known and described in the chemical literature, and some of them are available commercially.

Among the numerous references pertaining to these compounds are the following articles:

(1) Metal Boron Hydn'des, William V. Hough and Lawrence J. Edwards, Advances in Chemistry Series, American Chemical Society, No. 32, 184 (1961).

(2) Chemistry of Boranes, V. D. Aftandilian et al., Inorg. Chem. 1 No. 4, 734 (1962).

(3) Chemistry of Boranes, E. L. Muetterties, Inorg. Chem. 2 NO. 3, 647 (1963).

(4) Chemistry of Boranes, E. L. Muetterties et al., Inorg. Chem. 3 No. 3, 444 (1964).

(5) Polyhedral Boranes, E. L. Muetterties and W. H. Knoth, Chem. & Eng. News, 88, May 9, 1966.

Variations in the cations of these compounds can be made by using either metathesis reactions or cation exchange technics well known in the art.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. In the reversal step of a photographic reversal process in which a photographic element is contacted with a nucleating agent for sufficient time to nucleate the previously unexposed silver halide and render it developable to a visible positive image upon contact with a developer, the improvement comprising the step of nucleating the said previously unexposed silver halide by contacting said photographic element with an aqueous solution of an ionic boron hydride the anion of which is a member selected from the group consisting of B H B H B H and B H said aqueous solution containing at least 10 milligrams of said boron compound per liter of solution.

2. In a method of producing a photographic color reproduction comprising exposing to a colored image a photographic element containing at least two photographic silver halide emulsion layers which have been differentially sensitized to different spectral regions, developing said photographic element to a negative black-and-white image by treatment with a photographic black-and-white developer, contacting said photographic element with a nucleating agent for sufficient time to nucleate previously unexposed silver halide and render it developable to a visible image upon contact with a second developer, and developing said photographic element in a photographic color developer solution in the presence of a color-forming compound which couples with the oxidation products of said photographic color developer to produce a colored image, the improvement comprising the step of nucleating said previously unexposed silver halide by contacting said photographic element with an aqueous solution of an ionic boron hydride the anion of which is a member selected from the group consisting of B H B1QH10=, B11H14 and B zH z Said aqueous solution COH- taining at least 10 milligrams of said boron compound per liter of solution.

3. In a method of reproducing a photographic color reproduction comprising exposing to a colored image a photographic element comprising a support having coated thereon three photographic silver halide emulsion layers, one of said layers being sensitive to the red region of the spectrum and having dispersed therein a cyan-image-forming coupler, one of said layers being sensitive to the green region of the spectrum and containing a magenta-image-forming' coupler, and a third one of said layers being sensitive to the blue region of the spectrum and containing a yellow-image-forming coupler, developing said photographic element in a photographic black-and-white developer to produce a negative image, contacting said photographic element with a nucleating agent for a sufficient time to nucleate the previously unexposed silver halide and render it developable to a visible image by developing said element in a photographic phenylene-diamine color developer to produce colored images bearing a complementary relationship to the color in the original being reproduced, contacting said photographic element with a photographic clearing and fixing bath, contacting said element with an oxidizing bath to remove residual silver salts from said photographic silver halide emulsion layers, the improvement comprising the step of nucleating said previously unexposed silver halide by contacting said photographic element with an aqueous solution of an ionic boron hydride the anion of which is a member selected from the group consisting of B3H3' B t-I F, B11H14 and B H and the cation of which is derived from an atom selected from the class consisting of nitrogen, sulfur, phosphorus, arsenic, antimony, an alkali metal and an alkaline earth metal; said aqueous solution containing at least 10 milligrams of said boron compound per liter of solution.

4. A photographic reversal process of claim 3 in which the step of nucleating the photographic element is accomplished by treating the said element with the aqueous solution of the boron compound nucleating agent before contacting the said element with the photographic color developer solution.

5. A photographic reversal process of claim 3 in which the step of nucleating and color developing the photographic element is accomplished by treating the said element in the photographic color developer to which has been added at least 10 milligrams of the said boron compound nucleating agent per liter of said developer.

6. An aqueous nucleating bath for use in reversal processing of silver halide photographic elements, said nucleating bath having a pH in the range from about 3 to about 13 and containing, as a silver halide nucleating agent, at least 10 milligrams per liter of solution of an ionic boron hydride the anion of which is a member selected from the group consisting of B H B H 11 1f, and 12 12 7. An aqueous nucleating bath as described in claim 6 wherein the cation of said ionic boron hydride is derived from an atom selected from the class consisting of nitrogen, sulfur, phosphorus, arsenic, antimony, an alkali metal and an alkaline earth metal.

8. An aqueous nucleating bath as described in claim 7 wherein said nucleating agent is present in an amount of from about 70 to about 400 milligrams per liter.

9. An aqueous nucleating bath as described in claim 7 wherein said nucleating agent is tetramethylammonium octahydrotriborate.

10. An aqueous developing solution for use in reversal processing of silver halide photographic elements, said developing solution comprising about 0.5 to about 15 grams per liter of a silver halide developing agent and, as a silver halide nucleatin agent, at least 10 milligrams per liter of an ionic boron hydride the anion of which is a member selected from the group consistin of B H ro io 11 14 and 12 12 11. An aqueous developing solution as described in claim 10 wherein the cation of said ionic boron hydride is derived from an atom selected from the class consisting of nitrogen, sulfur, phosphorus, arsenic, antimony, an alkali metal and an alkaline earth metal.

12. An aqueous developing solution as described in claim 11 wherein said nucleating agent is present in an amount of from about 70 to about 400 milligrams per liter.

13. An aqueous developing solution as described in claim 11 wherein said nucleating agent is tetramethylammonium octahydrotriborate.

14. An aqueous developing solution as described in claim 11 wherein said silver halide developing agent is a primary aromatic amino color developing agent.

15. An aqueous developing solution as described in claim 11 wherein said silver halide developing agent iS 9 10 4-amino-N-ethy1-N-(IS-methane sulfonamido ethyl)-m- Chemistry 2nd ed., Interscience Publishers, New York, toluidine sesquisulfate monohydrate. 1969. pps. 281-284.

N. E. Miller, H. C. Miller, and E. L Muetterties, In-

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OTHER REFERENCES 10 66 F. A. Cotton & G. Wilkinson, Advanced Inorganic 

